Specialized containment vessels for storing solids, liquids, and gases are known in the prior art. These prior art containment vessels have been utilized for containment of solid rocket engine propellants, liquids in the form of jet fuels, and gases such as oxygen. These specialized containment vessels are often constructed of lightweight, high strength materials for use in various environments including aircraft and space vehicle environments. In general, it has been found that these prior art containers are often unsatisfactory because they deteriorate, are destroyed, or are too porous to contain the very substance the container was designed to store. In military aircraft applications, for example, jettisonable external aircraft fuel tanks have been conventionally constructed of a lightweight metal, such as aluminum. These aluminum tanks are utilized for extending the range of military aircraft. The recent need for a survivable, external aircraft fuel containment vessel has resulted in the construction of containment vessels that are not all metallic and has generated the production of tanks on a limited scale that utilize lightweight, high strength plastic materials. These survivable tanks have been constructed of various materials and combinations of materials, and require an internal liner that is compatible with the stored fuels. The known survivable, external aircraft fuel tanks have utilized aluminum as an internal liner with a structural outer shell applied by wrapping the aluminum liner with glass filaments bonded together and to the aluminum liner with an epoxy resin. The metal lined fuel tank has been found to be heavy for military aircraft, and does not meet all the specifications of a non-metallic containment vessel. Containment vessels in the form of survivable, external, aircraft fuel tanks have been constructed without utilizing metallic liners, and employing an outer shell constructed of a composite honeycomb structure having fiberglass filaments wound under and over the honeycomb structure with a plastic internal liner compatible with aircraft fuels. These prior art plastic liners have either been constructed as a laminated plastic or rotationally molded plastic. A thick liner wall is required in order to provide a reliable leaktight plastic liner by these prior art manufacturing techniques. The thickness of the plastic liners is so great that it adds an undesirable amount of weight to the containment vessel or aircraft fuel tank. The liner is also expensive to manufacture due to section seam bonding and resulting excessive quality control required.
There has also been developed in the past, containment vessels for non-fuel liquids for internal use aboard aircraft. A containment vessel for internal use aboard aircraft need not have an aerodynamically smooth outer surface, as is required on an external aircraft fuel tank. The requirement for an aerodynamic smooth outer surface on an external aircraft fuel tank renders it necessary to place the structural members or load carrying members and reinforcing members for the outer shell of the tank within the tank to achieve a streamlined outer surface. The prior art internal aircraft liquid tanks that have been developed heretofore utilize a smooth plastic inner liner compatible with the liquid. The outer shell is reinforced with the structural members arranged on the outside of the tank. One such aircraft containment vessel, used for storing drinking water aboard commercial aircraft, utilizes a seamless A.B.S. plastic liner thermally formed into the shape of the interior of the containment vessel. This liner is formed from A.B.S. tubing that has been extruded under high pressure. Metal liners have also been employed in such applications which are fabricated with welded, bonded, or mechanically fastened joints, and are therefore not seamless. Known A.B.S. plastics are not comptible with aircraft fuel additives and, therefore, can't be employed for external aircraft fuel tanks. Accordingly, there is a present need for a lightweight, high strength containment vessel having a relatively lightweight plastic liner that is formable, reliable, inexpensive, leakproof, and is compatible with the stored liquid, gases, or solids, including aircraft fuels having fuel additives therein.